There are three parts to testing for hepatitis C virus (HCV). The first test, the HCV antibody test, determines whether you have been exposed to the virus. The second test is the viral load test, which detects whether you were merely exposed or actually have HCV. If that test is positive, then a genotype test is done to find out what kind of HCV you have.
HCV Antibody Testing: Antibodies to HCV can be detected in the blood, usually within two to three months after the virus enters the body. If a person is positive for HCV antibodies, he or she has been exposed to the virus in the past. About 15 to 25 percent of people who are initially infected with HCV are able to clear the virus from their bodies, usually within six months of exposure, so the next step is to look for the actual virus in the bloodstream, using a viral load test. If a person has an acute infection, meaning that he or she was recently infected with HCV, antibodies may not have formed yet, so a viral load test is necessary to confirm infection.
HCV Viral Load Testing: A health care provider can request a qualitative HCV RNA test to determine whether the virus is in a person’s bloodstream. The HCV RNA test can also figure out a person’s HCV viral load (the amount of HCV in a measurement of blood).
HCV viral load testing is used during treatment to determine how well the medications are working. Increases and decreases in HCV RNA do not correlate to disease progression, so the qualitative viral load test is not very useful outside of treatment. HCV viral load results cannot determine whether or when someone with hepatitis C will develop cirrhosis or liver failure.
HCV Genotypic Testing: HCV has seven different genotypes, which are numbered in the order of their discovery. Each of these genotypes has subtypes, which are lettered in the order that they were discovered. It is important to find out which hepatitis C genotype you have because it determines the best treatment for you. People with genotype 1a may need screening for certain viral genetic variations (NS5A polymorphisms) prior to starting treatment to determine dosage duration.